This invention relates generally to apparatus for performing tests on fluids, such as cement to be pumped into a well, and more particularly, but not by way of limitation, to compact, transportable apparatus for performing static gel strength, thickening time and compressibility tests on a sample of cement.
In the oil and gas industry, different fluids are used for various purposes in drilling and completing a well. For example, batches of cement must be made and pumped into the well for cementing the casing into the well bore. The cement is generally pumped through the casing for flow back up the annulus between the well casing and the well bore to create the necessary bond.
Because different batches of fluids can have different characteristics which affect how the fluids perform in the high temperature and high pressure environments found downhole, there is the need for equipment which can perform different tests on a fluid sample prior to the fluid being pumped downhole so that one can determine if that particular batch of fluid has the proper characteristics for the particular situation. For example, three characteristics of fluid cement are known to be important. One is the static gel strength, or more specifically, the time it takes a static quantity of the cement to reach a predetermined gel strength. The static gel strength is important to know because it relates to the ability of the cement to prevent gas leaks when the cement is flowed into the annulus. If the cement will not properly gel, gas may create channels through the cement to the surface causing a hazardous situation. The static gel strength also relates to the ability of the cement to flow, which indicates how long the cement slurry can be pumped. Another important characteristic is the thickening time for the cement to reach a predetermined thickness or consistency. This characteristic also relates to how long the cement can be flowed before it begins to set up. Still another important characteristic to know is the compressibility of the cement. This characteristic is also pertinent to the gas leakage considerations for which the static gel strength test is performed. However, the compressibility test determines the hydrogen content resulting from additives in the cement slurry, which hydrogen content allows one to determine the shrinkage or swelling to be expected as the cement is flowed into the well and sets up. Because these characteristics vary with respect to different pressures and temperatures, there is the need for equipment with which these tests can be conducted under selectable pressures and temperatures simulating the environments in which the particular batch of fluid will be used.
The desirability of performing such tests on fluids, such as cement, has been known. Various types of equipment have also been built and used to perform one or more of these tests. For example, consistometers for measuring thickening time and viscometers for measuring viscosity have been used. We are aware that Halliburton Services has performed static gel strength, thickening time and compressibility tests on cement samples, in particular. However, we are not aware of a compact and transportable apparatus which performs these three specific functions with the components combined in the manner described and claimed herein.